Shipwreck's part in some inconclusive or specious argument (7)
I believe the answer is:
sophism
'specious argument' is the definition.
(I've seen this before)
'shipwreck's part in some inconclusive' is the wordplay.
'shipwreck' becomes 'phis' (anagram of 'ship').
'part in' is an insertion indicator (inserted letters form part of the word).
'inconclusive' means to remove the last letter.
'some' with its last letter taken away is 'som'.
'phis' going within 'som' is 'SOPHISM'.
'or' acts as a link.
(Other definitions for sophism that I've seen before include "faulty reasoning" , "False argument" , "specious argument" .)